Louisville residents searching for the source of an unexplained ground-shaking boom can scratch another theory off the list.

A Loudon County resident speculated on Thursday that the noise could have come from maintenance on an underground pipeline (see previous story below). The Plantation Pipe Line Company operates a large liquid refined petroleum pipeline that runs from Knoxville to Macon, Georgia. The pipeline is co-owned and operated by Kinder Morgan.

Emily Mir with Kinder Morgan's media relations department contacted 10News on Friday morning and indicated there were no recent operations that would have created the noise. Furthermore, the pipeline in question is located around 10 miles from the Lashbrooke subdivision.

The Lashbrooke subdivision in Louisville enjoyed a quiet and sun-bathed afternoon on Thursday. The peaceful surroundings of the affluent neighborhood along the Tennessee River lend no hint that its residents suffer from shell-shock.

"It's scary-loud. It's loud enough that it makes your heart stop for a second," said Andy Wombold. "It sounds like a shotgun or an explosion of some kind."

Wombold and dozens of other residents in the neighborhood are unable to say exactly what "it" is. All they know is the mysterious booms have provided several rude awakenings that sent residents scrambling in fear.

"Last Monday, about a week and a half ago, it was around 3 a.m. and it was, 'Pow!' All the sudden we heard a loud explosion. It sounded like it came from inside our house. It shook the walls. It shook the floor. It shook the ceiling," said Wombold.

Wombold said he ran upstairs to check on his parents and ran into his father who was already headed downstairs.

"We thought maybe a gas line had exploded and maybe our house was going to blow up. We thought it was really serious," said Wombold.

"It was like lightning struck directly beside the house," said neighbor Dwayne Jones. "I jumped out of bed and ran outside. Then I saw a clear sky full of stars and knew it wasn't lightning. The ground was still shaking for a little bit. It was like a big sonic boom. Just the whole house shakes. I never heard anything like it."

Several residents called emergency dispatchers and Blount County deputies responded to the scene. However, they were unable to find any problems in the neighborhood. Marian O'Briant with the Blount County Sheriff's Office said deputies also checked with local rock quarries and confirmed there were no blasting operations.

Residents said the booms continued for several days.

"It would happen in the middle of the night, in the morning, at all different times," said Jones. "It was like they would get a little weaker as the days went by, but it was still really jarring."

"You generally heard one big boom and then a bunch of aftershocks in quick succession. I don't know if it was an echo off the river or what," said Wombold.

A Tennessee National Guard spokesman confirmed there were no military operations in the area that would create the ground-shaking experience.

T-DOT told 10News there are no construction projects in the area that could explain the noise.

The USGS said there has only been one earthquake in Tennessee in the last couple of weeks. That tremor only registered 1.4 on the Richter magnitude scale and was in Tiptonville along the Mississippi River.

"The other thing we figured is it might have been something with the power lines," said Jones. "We have these very large lines that go directly through the neighborhood and across the river, but we never had any power outages."

TVA confirmed there have been no problems with the lines near the Lashbrooke subdivision.

The mystery may be more difficult to solve as the frequency of the booms decreases. Wombold said it has been a couple of days since he last heard a boom while Jones indicated he has not noticed the noise since late last week. Blount County dispatchers said the last call they received about the booms was last week.

Whatever the cause, residents said the booms repeatedly sent an unforgettable and shocking experience through the neighborhood for most of the week.

"Be sure to lock your doors because who knows where that noise is coming from," joked Wombold. "I just really want to know what caused it."

Pipeline "Pigging" Possibility?

A Loudon County resident provided another theory about the source of the explosive sounds. Greg Potter from Lenoir City said he had a similar experience a few years ago.

"One night we heard all kinds of booms. It shook the house and the ground," said Potter. "We called the police. We eventually found out there was a pipeline that runs deep underground in our yard. The pipeline company was doing what they called 'pigging' where they shoot something like nitrogen slugs between the product to clear the pipeline."

The Plantation Pipeline Company (PPC) operates a large pipeline that runs from Knoxville to Loudon and continues to Chattanooga before ending in Macon, Georgia. PPC is co-owned and operated by Kinder Morgan. 10News contacted the company and is awaiting a response to see if any recent operations could have created the noise in Louisville.